Electron discharge devices



Oct. 1, 1957 G. H. ROBERTSON 2,808,533

ELECTRON DISCHARGE DEVICES Filed Feb. 8, i952 2 Sheejzs-Sheet 2 IN VEA/70k a. H ROBE-R 7's0/v A 7' TORNE Y United States Patent Office2,808,533 Patented Oct. 1, 1957 ELECTRON DISCHARGE DEVICES George H.Robertson, Summit, N. IL, assignor to Bell Telephone Laboratories,Incorporated, New York, N. Y., a corporation of New York ApplicationFebruary 8, 1952, Serial No. 270,598

11 Claims. (Cl. 3153.5)

This invention relates to traveling wave tubes and more particularly tosuch tubes wherein coaxial input and output terminals are utilized forthe transfer of high frequency energy between the tube and associatedtransmission systems.

In such devices the high frequency energy is introduced into the tube atthe electron gun end of the tube, coupled to the helix, removed from thehelix at the electron collector end of the tube, and transferred fromthe tube to an associated output transmission line or system.

A general object of this invention is to improve the coupling of highfrequency energy between coaxial terminals and a helix of a travelingwave tube.

It is a further object of this invention to provide improved coaxialterminals wherein the electron gun and electron receiver assemblies arefacilely supported within the inner conductors of the coaxial terminals.

These and other objects of this invention are achieved in one specificillustrative embodiment of this invention wherein the outer conductor ofthe coaxial terminal comprises an outer cup-shaped member having anaperture in its base and the inner conductor of the coaxial terminalscomprises an inner cup-shaped member to which the helix is connected,the helix extending through the aperture close to the edge of the baseso that the edge and end of the inner cup-shaped member define a gap ofhigh electric field intensity having a large axial component forcoupling the electromagnetic energy between the transmission linedefined by the helix and the transmission line defined by the inner andouter cup-shaped members of the coaxial terminal. There will also be aradial electric field between this edge and the portion of the helixdirectly adjacent thereto. However, this radial field will not beinvolved in the coupling of the high frequency energy between thecoaxial terminal and the helix of the traveling wave tube.

In this specific illustrative embodiment, the electrode assemblies arepositioned and supported within the inner cup-shaped member of thecoaxial terminals. Thus the electron gun assembly is positioned withinthe inner cupshaped member of the coaxial inputterminal, and theelectron collector assembly is positioned within the inner cup-shapedmember of the coaxial output terminal.

It is, therefore, one feature of this invention that the helix of atraveling wave tube be electrically connected to the inner conductor ofa coaxial terminal and extend closely through an aperture in a memberdefining a portion of the outer conductor of the coaxial terminal, the

end of the inner conductor and the edge of the member adjacent theretodetermining a gap having an electric field of high intensity having alarge component along the axis of the helix for the coupling ofelectromagnetic energy between the helix and the coaxial terminal.

It is a further feature of this invention that the coaxial terminal of atraveling wave tube comprise a pair of cupshaped members, the innercup-shaped member being a' portion of the inner conductor of the coaxialterminal and the outer cup-shapedrnember being a portion of the outertion of the following detailed description and the accom-,

panying drawing, in which:

Fig. 1 is a sectional view of a portion of a traveling wave tubeillustrative of one specific embodiment of this invention showingparticularly the coaxial input terminal and electron gun assembly;

Fig. 2 is a plan view taken along the line 22 of Fig. 1 showingparticularly the gap of high field concentration defined by the helixand the outer cup-shaped member for the coupling of electromagneticenergy from the input terminal to the helix;

Fig. 3 is a sectional view of another portion of the traveling Wave tubeof Fig. 1 showing particularly the coaxial output terminal and theelectron collector assembly; and

Fig. 4 is an external view of a traveling wave tube of which Fig. 1 is asectional view of the input terminal and gun assembly and Fig. 3 is asectional view of the output terminal and collector assembly.

Referring now to the drawing, the specific illustrative embodiment ofthis invention there depicted comprises a cylindrical ceramic tube 10extending between two cupshaped metallic members 11 and 12 and sealedthereto to form a portion of the envelope of the device. The tube mayadvantageously be of a ceramic known as F-66 Steatite and may be sealedto the metallic members by the method disclosed in application SerialNo. 220,575, filed April 12, 1951, by A. l. Chick and L. J. Speck, nowPatent 2,708,787, May 24, 1955. Alternatively, the tube 10 may bemetallic. Cup-shaped metallic member 11, as best seen in Fig. 1,encompasses and supports the electron gun assembly and input terminal ofthe device, and cup-shaped metallic member 12, as best seen in Fig. 3,encompasses and supports the electron receiver assembly and outputterminal of the device.

The outer conductor of the input coaxial terminal comprises the outercup-shaped member 11, an end closure cap 14 extending across the end ofthe cup-shaped member 11 and hermetically sealed thereto, as by brazing,and an elongated tube 15, preferably integral with cap 14. The innerconductor of the input coaxial terminal comprises an inner conductor 16positioned by a glass or ceramic head 18 within the tube 15, theconductor having spring fingers 17 at each end adapted to fit over amating conductor, and an inner cup-shaped member 20 in which ispositioned the electron gun assembly 21, a closure cap 22 fitting overthe end of the inner cup-shaped member 20 and having a finger 23preferably integral therewith extending into the spring fingers 17 ofinner conductor 16. A sleeve 25 extends, preferably integrally, from thebase of the inner cup-shaped member and provides support for one end ofthe helix support rods 26 which are advantageously glazed to the sleeve.The helix 27, which may be advantageously glazed to the support rods 26,is electrically connected, as at 28, to the sleeve 25 so that acontinuous electrical connection is provided from the inner conductor 16to the helix 27.

The helix 27 and rods 26 extend through an aperture 36 in the base ofthe outer cup-shaped member 11, the aperture being shaped to have itsedge closely adjacent the helix, as by being circular with cut-outportions 31 to allow passage therethrough of the helix support rods 26,as best seen in Fig. 2. The electromagnetic energy is guided from theexternal transmission line, Whether of a wave guide or coaxial linetype, to the coaxial input terminal by a coaxial jack 33having its innerconductor 3 extending into the spring fingers 17 of the inner condoctor16 and its outer conductor 35 threadedly engaged to a connecting ring 36secured to the outside of the tube 15. The electromagnetic energy isthen guided by the coaxial input terminal to the gap defined by the endof .the sleeve 25 and the aperture 30 in the base of the outercup-shaped member 11. As the sleeve 25 is electrically a part of theinner conductor of the coaxial input terminal and the base of the outercup-shaped member 11 is electrically a part of the outer conductor ofthe coaxial input terminal, an electrical field of high intensity existsacross this gap. This field has a component along the axis of the helixthat couples the electromagnetic energy from the transmission linedefined by the inner and outer conductors of the coaxial input terminalto the transmission line defined by the helix 27.

In this specific embodiment of this invention, the inner cup-shapedmember 20, which is a portion of the inner conductor of the coaxialinput terminal, is positioned from the outer cup-shaped member 11, whichis a portion of the outer conductor .of the coaxial input terminal, by alarge insulating ring 39 having a dished portion 40 into which the baseof the inner cup-shaped member fits. The electron gun assembly 21 issupported within the inner cup-shaped member by a plurality of insulatorrings 41 which position the cathode assembly 42 and the acceleratingelectrode 43, certain of the rings 41 being dished to prevent transversemotion of these elements. A plurality of springs 44 bear against theinsulator rings 41 and bias them against the base of the innercup-shaped member 20.

The cathode assembly 42 advantageously comprises a disc 47 having anelectron emissive coating thereon, a tubular heater cup 48 across whichthe disc 47 extends, a heater element 49 within the heater cup 48, abase member 50 to which the heat shield is connected by a plurality ofstrips 51, and a cylindrical heat shield 52 having a flanged portion 53held in a dished portion of one of the insulator rings 41, thecylindrical heat shield 52 being secured at its base, as by welding, tothe base member 50.

Leads 55 are connected to the cathode assembly 42, the acceleratingelectrode 43, and the ends of the heater element 49 and extend throughapertures 56 in the inner cup-shaped member 20. Positioned in the outercupshaped member 11 opposite each of the apertures 56 is a terminal pin58 extending through a glass or ceramic bead 59. The direct currentconnections to the elements of the electron gun assembly are provided byconnecting the leads 55 to the terminal pins 58, getters 68 also beingadvantageously connected between the leads 55 and the inner wall of theouter cup-shaped member 11 and being burned out during the processing ofthe device. A high frequency filter 62 is connected between the terminalpins 58 and the outer cup-shaped member 11 to prevent passage of theradio frequency power to the direct current supplies and comprises ashell 64 positioned with its base on the outer cup-shaped member 11, apair of button condensers 65 electrically connected between the terminalpin 58 and the shell 64, and a choke 66 between the capacitances 65 andcomprising a few turns of wire within the shell 64.

The inner cup-shaped member 20 is held in position by a spring washer 68in the closure cap 14; the washer 68 bears against an insulating annulus69 having a central aperture 70 therein for passage of the finger 23therethrough, thereby biasing the inner cup-shaped member 20 against thelarge insulator ring 39 and the base of the outer cupshaped member 11.

The coaxial output terminal, as best seen in Fig. 3, similarly comprisesan outer conductor defined by the outer cup-shaped member 12 and aclosure cap 71 therefor, the closure cap having a tubular portion 72integral therewith, and an inner conductor defined by conductor 73within the tubular portion 72 and separated there- 4 from by a glass orceramic bead 74, an inner cup-shaped member 75, and a closure'cap 76therefor. A finger 77, preferably integral with" the closure cap 76,extends through an insulator annulus 78 and into mating spring fingers79 on the end of conductor 73. A sleeve 81 preferably integral with theinner cup-shaped member 75, supports the other end of the helix supportrods 26. Advantageously, the sleeve 81 is slotted to fit closely withina metallic ring 82 secured, as by glazing, to the rods 26. The helix 27is connected to the ring 82 so that electrical connection to the sleeve81 is secured thereby. Thus, in the assembling of the device, the helixand support rods may be assembled as a separate unit, secured to theinner cup-shaped member 28 of the coaxial input terminal, and insertedwithin the device. Connection may then be made to the inner cup-shapedmember 75 of the coaxial output terminal without requiring any brazingor glazing process, as the slotted portions of sleeve 81 will act asspring fingers and bear against the ring 82.

The base of the outer cup-shaped member 12. has an aperture 85 thereinshaped so that the helix 27 is closely adjacent theedge of the base ofthe member 12, the shape being similar to that of aperture 30, as seenin Fig. 2. Coupling of the electromagnetic energy from the transmissionline defined by the helix 27 to the transmission line defined by theinner and outer cupshaped members, which comprise the inner and outerconductors of the coaxial output terminal, is thus achieved by theelectrical field of high intensity existing across the predominantlyaxial gap between the end of the sleeve 82 and the edge of aperture 85in the outer cup-shaped member 12.

Positioned within the inner cup-shaped member 75 is the electronreceiving assembly 86 which comprises a suppressor electrode 87 and acollector electrode 88, these electrodes being held in place by dishedinsulators 89. Leads 91 extend from the suppressor and collectorelectrodes through apertures 92 in the inner cup-shaped member 75'toterminals 93 extending through glass or ceramic beads 94 sealed in theouter cup-shaped member 12. A lead conductor also advantageously extendsfrom the terminal 93 to the cup-shaped member 75 to apply a directcurrent potential to the helix 27. Filters 62 are secured to theterminals 93 external to the envelope of the device.

A plurality of springs 95 hold the insulators 89 and suppressor andcollector electrodes in position within the inner cup-shaped member 75,and a spring washer 96 bears against the insulator annulus 78 and biasesthe inner cup-shaped member 75 against an insulator ring 97 on the baseof'the outer cup-shaped member 12. As only three external leads need bebrought out from the electron receiver assembly within the innercup-shaped member 75, one aperture in the outer cup-shaped member 12opposite an aperture 92 in the inner cup-shaped member 75 can have anexhaust tubulation secured therein for evacuating the device.

' While the invention has been described with reference to a specificembodiment wherein the two outer cupshaped members are separate andjoined by an insulating tube, itis to be understood that they may bejoined by a metallic'tube and that the two outer cup-shaped membersandthe metallic tube may all be integral. I Such a metallic envelope hasthe advantage of providing shielding 'for the helix interaction space.

' Reference is made to application Serial No. 270,599, filed February 8,1952, by G. H. Robertson and E. J. Walsh, now Patent No. 2,765,421,issued October 2, 1956, and application Serial No. 270,721, filedFebruary 8, l952,'by J. R. Pierce, now Patent 2,761,915, issuedSeptember 4, 1956, wherein are described related inventions.

' It is to be understood that the above-described arrangements areillustrative of the application of the principles of the invention.Numerous other arrangements may be devised by those skilled in the artwithout departing from the spirit and scope of the invention.

What is claimed is:

1. An electron discharge device comprising a helix, a coaxial terminal,means for transferring electromagnetic energy between said helix andsaid terminal, said means comprising an outer hollow member comprising aportion of the outer conductor of said terminal and an inner hollowmember comprising a portion of the inner conductor of said terminalwithin said outer hollow member, said helix being electrically connectedto one of said hollow members, the end of said one hollow memberdefining with the other of said hollow members a gap having therein anelectric field in an axial direction in said helix, and an electrodeassembly positioned within said inner hollow member.

2. An electron discharge device comprising an envelope, a coaxialterminal extending through said envelope at each end thereof, acylindrical member electrically attached to the outer conductor of eachof said terminals, said cylindrical members each having an end platethereacross with an aperture therein, a helix extending in said envelopethrough said apertures closely adjacent the edge of said end platestherein, means within said cylindrical members electrically connectingsaid helix to the inner conductor of each of said coaxial terminals anddefining therewith a gap having an axial electric field therein,electron gun means positioned in one of said cylindrical membersopposite one end of said helix for projecting a stream of electronsalong said helix, and electron receiving means positioned opposite theother end of said helix in the other of said cylindrical members.

3. An electron discharge device comprising an envelope, a coaxialterminal extending through said envelope, a cylindrical memberelectrically attached to the outer conductor of said terminal, saidcylindrical member having an end plate with an aperture therein, a helixextending in said envelope and extending through said aperture closelyadjacent the edge of said plate therein, means within said cylindricalmember electrically connecting said helix to the inner conductor of saidcoaxial terminal and defining therewith a gap having an electric fieldtherein in the direction of the axis of said helix, and electrode meanspositioned within said cylindrical member opposite one end of saidhelix.

4. An electron discharge device comprising a helix, electron gun meansfor projecting a stream of electrons along said helix, means forcoupling electromagnetic energy to said helix, said last-mentioned meanscomprising an outer hollow member comprising a portion of the outerconductor of a coaxial terminal and having a base with an aperturetherein, and an inner hollow member within said outer hollow member,said helix being connected to said inner hollow member and extendingthrough said aperture closely adjacent the edge of said base in saidaperture, the end of said inner hollow member defining a gap with saidedge of said base in said aperture and means supporting said electrongun means within said inner hollow member.

5. An electron discharge device comprising a helix, a coaxial terminal,and means for transferring electromagnetic energy between said helix andsaid terminal, said means comprising an outer hollow member comprising aportion of the outer conductor of said terminal, said outer hollowmember having a base with an aperture therein, and an inner hollowmember positioned within said outer hollow member and comprising aportion of the inner conductor of said terminal, said helix beingelectrically connected to said inner hollow member and extending throughsaid aperture adjacent the edge of said base therein, and an electrodeassembly supported within said inner hollow member.

6. An electron discharge device comprising an outer cup-shaped memberhaving a base and an aperture centrally therein, an inner cup-shapedmember located within said outer cup-shaped member, electron gun meanssupported within said inner cup-shaped member and insulated therefrom, ahelix connected to said inner cupshaped member, means supporting saidhelix from said imier cup-shaped member, said helix extending throughsaid aperture closely adjacent said base, a coaxial terminal having aninner conductor connected to said inner cup-shaped member and an outerconductor connected to said outer cup-shaped member, and electronreceiver means adjacent the opposite end of said helix from saidelectron gun means.

7. An electron discharge device comprising an envelope, a pair ofcoaxial terminals positioned at opposite ends of said envelope, each ofsaid terminals comprising an inner and an outer conductor, an outercylindrical member connected electrically to the outer conductor of eachof said terminals, a plate extending across each of said outercylindrical members having a central aperture therein, an innercylindrical member positioned within each of said outer cylindricalmembers and electrically connected to said inner conductors of saidterminals, a helix extending within said envelope through each of saidapertures and electrically connected to each of said inner cylindricalmembers, electron gun means positioned within one of said innercylindrical members adjacent one end of said helix, and electronreceiver means positioned within the other of said inner cylindricalmembers adjacent the other end of said helix.

8. A traveling Wave tube comprising an envelope, a helix extending insaid envelope, a coaxial terminal, an outer cup-shaped member having anaperture centrally in the base thereof and comprising a portion of theouter conductor of said terminal, an inner cup-shaped member axiallypositioned Within said outer cup-shaped member and comprising a portionof the inner conductor of said coaxial terminal, means supporting saidhelix from said inner cup-shaped member, said helix extending throughsaid aperture closely adjacent said base, insulating means supportingsaid inner cup-shaped member from said outer cup-shaped member, anelectrode assembly within said inner cup-shaped member, and insulatingmeans supporting said electrode assembly within said inner cup-shapedmember.

9. A traveling wave tube comprising an envelope, a helix extendingwithin said envelope, a coaxial terminal at each end of said envelope,an outer cup-shaped member at each end of said envelope and comprising aportion of the outer conductors of said terminals, each of said outercup-shaped members having an aperture centrally in the base thereof, aninner cup-shaped member within each of said outer cup-shaped members andcomprising a portion of the inner conductors of each of said terminals,the axes of said helix and said cup-shaped members being coincident,means supporting said helix from said inner cup-shaped members, saidhelix extending through said apertures closely adjacent the edge of saidbase therein, each of said inner cup-shaped members defining with saidedges a gap having an electric field therein having a component in thedirection of the axis of said helix, an electron gun insulatinglypositioned in One of said inner cupshaped members for projecting astream of electrons along said helix, and electron receiving meanspositioned in the other of said cup-shaped members.

10. A traveling wave tube comprising a pair of outer cup-shaped members,a cylindrical member therebetween, a coaxial terminal closure cap acrossthe end of each of said outer cup-shaped members, said outer cup-shapedmembers, cylindrical member, and coaxial terminal closure caps definingthe envelope of said device, said outer cup-shaped members having anaperture centrally in the base thereof and being electrically connectedto the outer conductors of said coaxial terminal closure caps, an innercup-shaped member within each of said outer cup-shaped members andelectrically connected to 7 a the inner conductors of each of saidcoaxial terminal closure caps, means supporting said helix from, saidinner cup-shaped members, said helix extending through said apertureclosely adjacent the edge of said base, electron gun means insulatinglysupporting Within one of said inner cup-shaped members for projecting astream of electrons along said helix, and electron receiving meanspositioned within the other of said inner cup-shaped members.

11. A traveling Wave tube comprising a pair of conducting outercup-shaped members, each of said members having an aperture axially inthe base thereof, a tubular member between said outer cup-shapedmembers, a conducting closure cap across the end of each of said outercup-shaped members, said closure cap comprising a coaxial sleeveportion, a conducting inner cup-shaped member withineach of said outercup-shaped members, means electrically connecting said inner cup-shapedmembers to the inner conductors of saidcoaxial sleeve portions, meanssupporting said inner cup-shaped members from said outer cup-shapedmembers comprising a dished insulating ring on the base of said outercup-shaped members and a spring washer biasing said inner cupshapedmembers against said insulating rings, a helix extending, in saidtubular member and through said apertures closely adjacent the edge orsaid bases therein, means supporting said helix from said innercup-shaped members, the axes of said helix, said inner, and said outercup-shaped members being coincident, electron gun means positioned inone of said inner cup-shaped members for projecting a stream ofelectrons along said helix, and electron receiving means positioned inthe other of said inner cupshaped members.

References Cited in the file of this patent UNITED STATES PATENTS HuberFeb. 1, 1955

